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I am having trouble querying a database from within an EJB. The code is as follows:

@Override
public boolean register(User user) {
// We have servlets that validate these fields, so we don't validate anything here
// We check to see whether there is already a user with the same user name or not
Query query = (Query) entityManager.createQuery("SELECT u FROM User u WHERE u.username=:userName"); // Exception is thrown at this point
((javax.persistence.Query) query).setParameter("userName", user.getUsername());
// We check each returned value. If we find anything than we do not add the user
List<User> users = castList(User.class, ((javax.persistence.Query) query).getResultList());
if(users.isEmpty()) {
// The user is not present. Add this user
entityManager.persist(user);
// return "Welcome to BooksPoint " + user.getUsername() + "!";
return true;
} else {
// return "Cannot create " + user.getUsername() + ". A user with this name already exists";
return false;
}
}

The exception thrown is:

18:42:34,878 ERROR [org.jboss.ejb3.invocation] (http-localhost-127.0.0.1-8080-1) JBAS014134: EJB Invocation failed on component UserViewBean for method public abstract boolean books.pointejb.UserViewBeanRemote.register(books.pointejb.User): javax.ejb.EJBException: java.lang.ClassCastException: org.hibernate.ejb.QueryImpl cannot be cast to javax.management.Query
at org.jboss.as.ejb3.tx.CMTTxInterceptor.handleExceptionInOurTx(CMTTxInterceptor.java:166) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.as.ejb3.tx.CMTTxInterceptor.invokeInOurTx(CMTTxInterceptor.java:230) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.as.ejb3.tx.CMTTxInterceptor.required(CMTTxInterceptor.java:304) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.as.ejb3.tx.CMTTxInterceptor.processInvocation(CMTTxInterceptor.java:190) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ejb3.remote.EJBRemoteTransactionPropagatingInterceptor.processInvocation(EJBRemoteTransactionPropagatingInterceptor.java:80) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ejb3.component.interceptors.CurrentInvocationContextInterceptor.processInvocation(CurrentInvocationContextInterceptor.java:41) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ejb3.component.interceptors.LoggingInterceptor.processInvocation(LoggingInterceptor.java:59) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ee.component.NamespaceContextInterceptor.processInvocation(NamespaceContextInterceptor.java:50) [jboss-as-ee-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ejb3.component.interceptors.AdditionalSetupInterceptor.processInvocation(AdditionalSetupInterceptor.java:32) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ee.component.TCCLInterceptor.processInvocation(TCCLInterceptor.java:45) [jboss-as-ee-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.invocation.ChainedInterceptor.processInvocation(ChainedInterceptor.java:61) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ee.component.ViewService$View.invoke(ViewService.java:165) [jboss-as-ee-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.as.ejb3.remote.LocalEjbReceiver.processInvocation(LocalEjbReceiver.java:179) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.ejb.client.EJBClientInvocationContext.sendRequest(EJBClientInvocationContext.java:179) [jboss-ejb-client-1.0.5.Final.jar:1.0.5.Final]
at org.jboss.ejb.client.TransactionInterceptor.handleInvocation(TransactionInterceptor.java:43) [jboss-ejb-client-1.0.5.Final.jar:1.0.5.Final]
at org.jboss.ejb.client.EJBClientInvocationContext.sendRequest(EJBClientInvocationContext.java:181) [jboss-ejb-client-1.0.5.Final.jar:1.0.5.Final]
at org.jboss.ejb.client.ReceiverInterceptor.handleInvocation(ReceiverInterceptor.java:128) [jboss-ejb-client-1.0.5.Final.jar:1.0.5.Final]
at org.jboss.ejb.client.EJBClientInvocationContext.sendRequest(EJBClientInvocationContext.java:181) [jboss-ejb-client-1.0.5.Final.jar:1.0.5.Final]
at org.jboss.ejb.client.EJBInvocationHandler.doInvoke(EJBInvocationHandler.java:136) [jboss-ejb-client-1.0.5.Final.jar:1.0.5.Final]
at org.jboss.ejb.client.EJBInvocationHandler.doInvoke(EJBInvocationHandler.java:121) [jboss-ejb-client-1.0.5.Final.jar:1.0.5.Final]
at org.jboss.ejb.client.EJBInvocationHandler.invoke(EJBInvocationHandler.java:104) [jboss-ejb-client-1.0.5.Final.jar:1.0.5.Final]
at com.sun.proxy.$Proxy22.register(Unknown Source)
at books.point.Register.doPost(Register.java:284)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:754) [jboss-servlet-api_3.0_spec-1.0.0.Final.jar:1.0.0.Final]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:847) [jboss-servlet-api_3.0_spec-1.0.0.Final.jar:1.0.0.Final]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:329)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:275)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:161)
at org.jboss.as.jpa.interceptor.WebNonTxEmCloserValve.invoke(WebNonTxEmCloserValve.java:50) [jboss-as-jpa-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.as.web.security.SecurityContextAssociationValve.invoke(SecurityContextAssociationValve.java:153)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:155)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:368)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:877)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:671)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:930)
at java.lang.Thread.run(Unknown Source) [rt.jar:1.7.0_45]
Caused by: java.lang.ClassCastException: org.hibernate.ejb.QueryImpl cannot be cast to javax.management.Query
at books.pointejb.UserViewBean.register(UserViewBean.java:44) [BooksPointEJB.jar:]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) [rt.jar:1.7.0_45]
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) [rt.jar:1.7.0_45]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) [rt.jar:1.7.0_45]
at java.lang.reflect.Method.invoke(Unknown Source) [rt.jar:1.7.0_45]
at org.jboss.as.ee.component.ManagedReferenceMethodInterceptorFactory$ManagedReferenceMethodInterceptor.processInvocation(ManagedReferenceMethodInterceptorFactory.java:72) [jboss-as-ee-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.invocation.WeavedInterceptor.processInvocation(WeavedInterceptor.java:53) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ee.component.interceptors.UserInterceptorFactory$1.processInvocation(UserInterceptorFactory.java:36) [jboss-as-ee-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.jpa.interceptor.SBInvocationInterceptor.processInvocation(SBInvocationInterceptor.java:47) [jboss-as-jpa-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.jpa.interceptor.SFSBInvocationInterceptor.processInvocation(SFSBInvocationInterceptor.java:58) [jboss-as-jpa-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ejb3.component.stateful.StatefulSessionSynchronizationInterceptor.processInvocation(StatefulSessionSynchronizationInterceptor.java:156) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.invocation.InitialInterceptor.processInvocation(InitialInterceptor.java:21) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.invocation.ChainedInterceptor.processInvocation(ChainedInterceptor.java:61) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ee.component.interceptors.ComponentDispatcherInterceptor.processInvocation(ComponentDispatcherInterceptor.java:53) [jboss-as-ee-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ejb3.component.stateful.StatefulComponentInstanceInterceptor.processInvocation(StatefulComponentInstanceInterceptor.java:66) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ejb3.tx.CMTTxInterceptor.invokeInOurTx(CMTTxInterceptor.java:228) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
... 44 more
18:42:34,952 ERROR [org.apache.catalina.core.ContainerBase.[jboss.web].[default-host].[/BooksPoint].[books.point.Register]] (http-localhost-127.0.0.1-8080-1) Servlet.service() for servlet books.point.Register threw exception: javax.ejb.EJBException: java.lang.ClassCastException: org.hibernate.ejb.QueryImpl cannot be cast to javax.management.Query
at org.jboss.as.ejb3.tx.CMTTxInterceptor.handleExceptionInOurTx(CMTTxInterceptor.java:166) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.as.ejb3.tx.CMTTxInterceptor.invokeInOurTx(CMTTxInterceptor.java:230) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.as.ejb3.tx.CMTTxInterceptor.required(CMTTxInterceptor.java:304) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.as.ejb3.tx.CMTTxInterceptor.processInvocation(CMTTxInterceptor.java:190) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ejb3.remote.EJBRemoteTransactionPropagatingInterceptor.processInvocation(EJBRemoteTransactionPropagatingInterceptor.java:80) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ejb3.component.interceptors.CurrentInvocationContextInterceptor.processInvocation(CurrentInvocationContextInterceptor.java:41) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ejb3.component.interceptors.LoggingInterceptor.processInvocation(LoggingInterceptor.java:59) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ee.component.NamespaceContextInterceptor.processInvocation(NamespaceContextInterceptor.java:50) [jboss-as-ee-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ejb3.component.interceptors.AdditionalSetupInterceptor.processInvocation(AdditionalSetupInterceptor.java:32) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ee.component.TCCLInterceptor.processInvocation(TCCLInterceptor.java:45) [jboss-as-ee-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.invocation.ChainedInterceptor.processInvocation(ChainedInterceptor.java:61) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ee.component.ViewService$View.invoke(ViewService.java:165) [jboss-as-ee-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.as.ejb3.remote.LocalEjbReceiver.processInvocation(LocalEjbReceiver.java:179) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.ejb.client.EJBClientInvocationContext.sendRequest(EJBClientInvocationContext.java:179) [jboss-ejb-client-1.0.5.Final.jar:1.0.5.Final]
at org.jboss.ejb.client.TransactionInterceptor.handleInvocation(TransactionInterceptor.java:43) [jboss-ejb-client-1.0.5.Final.jar:1.0.5.Final]
at org.jboss.ejb.client.EJBClientInvocationContext.sendRequest(EJBClientInvocationContext.java:181) [jboss-ejb-client-1.0.5.Final.jar:1.0.5.Final]
at org.jboss.ejb.client.ReceiverInterceptor.handleInvocation(ReceiverInterceptor.java:128) [jboss-ejb-client-1.0.5.Final.jar:1.0.5.Final]
at org.jboss.ejb.client.EJBClientInvocationContext.sendRequest(EJBClientInvocationContext.java:181) [jboss-ejb-client-1.0.5.Final.jar:1.0.5.Final]
at org.jboss.ejb.client.EJBInvocationHandler.doInvoke(EJBInvocationHandler.java:136) [jboss-ejb-client-1.0.5.Final.jar:1.0.5.Final]
at org.jboss.ejb.client.EJBInvocationHandler.doInvoke(EJBInvocationHandler.java:121) [jboss-ejb-client-1.0.5.Final.jar:1.0.5.Final]
at org.jboss.ejb.client.EJBInvocationHandler.invoke(EJBInvocationHandler.java:104) [jboss-ejb-client-1.0.5.Final.jar:1.0.5.Final]
at com.sun.proxy.$Proxy22.register(Unknown Source)
at books.point.Register.doPost(Register.java:284) [classes:]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:754) [jboss-servlet-api_3.0_spec-1.0.0.Final.jar:1.0.0.Final]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:847) [jboss-servlet-api_3.0_spec-1.0.0.Final.jar:1.0.0.Final]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:329) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:275) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:161) [jbossweb-7.0.13.Final.jar:]
at org.jboss.as.jpa.interceptor.WebNonTxEmCloserValve.invoke(WebNonTxEmCloserValve.java:50) [jboss-as-jpa-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.as.web.security.SecurityContextAssociationValve.invoke(SecurityContextAssociationValve.java:153) [jboss-as-web-7.1.1.Final.jar:7.1.1.Final]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:155) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:368) [jbossweb-7.0.13.Final.jar:]
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:877) [jbossweb-7.0.13.Final.jar:]
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:671) [jbossweb-7.0.13.Final.jar:]
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:930) [jbossweb-7.0.13.Final.jar:]
at java.lang.Thread.run(Unknown Source) [rt.jar:1.7.0_45]
Caused by: java.lang.ClassCastException: org.hibernate.ejb.QueryImpl cannot be cast to javax.management.Query
at books.pointejb.UserViewBean.register(UserViewBean.java:44) [BooksPointEJB.jar:]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) [rt.jar:1.7.0_45]
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) [rt.jar:1.7.0_45]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) [rt.jar:1.7.0_45]
at java.lang.reflect.Method.invoke(Unknown Source) [rt.jar:1.7.0_45]
at org.jboss.as.ee.component.ManagedReferenceMethodInterceptorFactory$ManagedReferenceMethodInterceptor.processInvocation(ManagedReferenceMethodInterceptorFactory.java:72) [jboss-as-ee-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.invocation.WeavedInterceptor.processInvocation(WeavedInterceptor.java:53) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ee.component.interceptors.UserInterceptorFactory$1.processInvocation(UserInterceptorFactory.java:36) [jboss-as-ee-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.jpa.interceptor.SBInvocationInterceptor.processInvocation(SBInvocationInterceptor.java:47) [jboss-as-jpa-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.jpa.interceptor.SFSBInvocationInterceptor.processInvocation(SFSBInvocationInterceptor.java:58) [jboss-as-jpa-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ejb3.component.stateful.StatefulSessionSynchronizationInterceptor.processInvocation(StatefulSessionSynchronizationInterceptor.java:156) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.invocation.InitialInterceptor.processInvocation(InitialInterceptor.java:21) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.invocation.ChainedInterceptor.processInvocation(ChainedInterceptor.java:61) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ee.component.interceptors.ComponentDispatcherInterceptor.processInvocation(ComponentDispatcherInterceptor.java:53) [jboss-as-ee-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ejb3.component.stateful.StatefulComponentInstanceInterceptor.processInvocation(StatefulComponentInstanceInterceptor.java:66) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288) [jboss-invocation-1.1.1.Final.jar:1.1.1.Final]
at org.jboss.as.ejb3.tx.CMTTxInterceptor.invokeInOurTx(CMTTxInterceptor.java:228) [jboss-as-ejb3-7.1.1.Final.jar:7.1.1.Final]
... 44 more

You have imported the class file incorrectly otherwise there was no need to provide the complete path of a class file in your 3rd line :- ((javax.persistence.Query) query).setParameter("userName", user.getUsername());
– Kumar AbhinavFeb 9 '14 at 18:18

Ohh dear.I think you have imported the wrong class file for Query.Just check your import or better put the complete code here.Check if you have imported javax.management.Query instead of javax.persistence.Query